The present invention relates to new 20,21-dinoreburnamenine derivatives, that is eburnamenine derivatives which unlike other eburnamenine derivatives do not contain an ethyl substituent (comprising the C.sub.20 and C.sub.21 atoms of the eburnamenine structure) attached to the heterocyclic structure, a process for their preparation and pharmaceutical composition thereof.
Eburnamine, a 14,15-dihydroeburnamenine-14-ol is a secondary alkaloid of the australian plant Hunteria eburnea Pichon (see, e.g., F. Bartlett et al, Compt. Rend. 240,1 (1955). A semisynthetic optical antipod of eburnamine, which exhibits vasodilatory properties is disclosed in the French Pat. No. 15 86 697.